A conventional plasma processing apparatus includes a processing chamber, a table disposed in the processing chamber, a dielectric window provided at the processing chamber, and a slot plate provided on the dielectric window. In this plasma processing apparatus, a substrate mounted on the table is processed by a plasma generated below the dielectric window by supplying a microwave to the slot plate. In other words, the slot plate and the dielectric window form a radial line slot antenna. When the microwave is irradiated to the antenna, the plasma is generated and various processes can be performed by using the plasma. Depending on types of gases used for plasma generation, various processes can be performed. In such an apparatus, etching or film formation is performed (see, e.g., International Publication No, WO2010/058642).
The conventional plasma processing apparatus has a problem that an inner surface of the processing chamber is etched or a contamination source generated by the etching of the inner surface of the processing chamber is deposited on the wafer W. In order to protect the inner surface of the processing chamber, the present inventors have suggested a surrounding body made of a dielectric material which surrounds a processing space between the table and the dielectric window to protect the inner surface of the processing chamber is protected.
When a bottom surface of the dielectric window has a recess and an opening end of the recess of the dielectric window has a downwardly protruding protrusion, the plasma generated in the recess of the dielectric window can be prevented from reaching the inner surface of the processing chamber by the protrusion.
However, the present inventors have found that the stability of the plasma deteriorates by the microwave propagation to the surrounding body in the plasma processing apparatus employing the surrounding body.